Submersible well pump assemblies (ESP) are frequently used to pump well fluid from hydrocarbon wells. A typical ESP has a pump driven by a motor. A seal section or pressure equalizer, normally located between the motor and the pump, has components to equalize pressure of lubricant contained in the motor with the hydrostatic pressure of the well fluid on the exterior of the ESP. Those components may be a flexible diaphragm, a bellows, or a labyrinth chamber.
A labyrinth chamber has a labyrinth tube extending downward from a connector or adapter on the upper end of the labyrinth chamber. The upper end of the labyrinth tube is open as well as the lower end, which is spaced a short distance above the lower end of the labyrinth chamber. A guide tube surrounds the drive shaft extending from the motor. The guide tube has a port near the upper end of the chamber. Lubricant from the motor flows up an annular clearance between the shaft and the guide tube and out the guide tube port into the labyrinth chamber. Well fluid flows down the labyrinth tube into the labyrinth chamber into contact with the lubricant. The well fluid applies the hydrostatic pressure on the exterior of the ESP to the lubricant in the labyrinth chamber, which communicates that pressure to lubricant in the motor. The well fluid has a higher specific gravity than the lubricant, thus is inhibited from flowing upward in the labyrinth chamber into the guide tube port to reach the guide tube port. It is important to keep the corrosive well fluid from flowing down the guide tube into the motor.
A labyrinth chamber works well in vertical wells and provides pressure compensation without any additional moving parts. However, if the pump is installed in a horizontal section of the well, the path from the outlet of the labyrinth tube to the guide tube port is approximately horizontal rather than being vertical. The well fluid entering the labyrinth chamber could more easily flow along the horizontal flow path than the labyrinth flow path that exists while the ESP is oriented vertically.